Changing carbon: Ice cores and proxies

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Scientists have made direct measurements of atmospheric carbon dioxide (CO2) levels for over 50 years. In addition to this, scientists investigate earlier CO2 levels by collecting samples of air trapped in ice cores extracted from the Antarctic ice sheet and from suitable glaciers around the world. The ice core data show that the concentration of CO2 in the atmosphere is higher today than it’s been for at least 800,000 years, and the rate of increase has been 100 times faster than any previous change in the ice core record. Other scientists use ‘proxies’, such as ancient sediments and leaf or plankton fossils, to estimate CO2 levels in even earlier periods.

Eric uses ancient ice to learn about climates past. He and his team spend ten weeks in chilly Antarctica, drilling deep into the polar ice. Once they’ve extracted the cores, they transport them to the laboratory in Cambridge for analysis. The content of trapped air bubbles, the amount of salt in the ice and other measurements reveal clues about the climate when the ice was formed. Eric works with experts around the world to unravel these clues and build up a picture of past climate changes. ‘Working out how our planet worked in the past gives us more confidence in predicting how it will behave in future,’ says Eric.